Integer Hash to a String Value

I want to compute Hash of a String, but the Hash value should be a number (long or integer).

In other words I want to compute integer hash of a string. Col开发者_运维知识库lusion resistance in not the concern.

Is there an way to convert MessageDigest of SHA-256 to a number.

I am using Java to accomplish this.

Try to call hashCode() method. It is already implemented and does exactly what you want.

Most obviously there is a hashCode() method on String

As for converting the MessageDigest to a number, you can either use hashCode again or take the byte array from the digest and compact this down to whatever size you want, integer, long or whatever with (say) xor.

public int compactDigest(MessageDigest digest) {
    byte [] byteArr = digest.digest();
    // +3 since conversion to int array with divide length by four.
    // and we don't want to lose any bytes.
    ByteBuffer bytes = ByteBuffer.allocate(byteArr.length + 3);
    bytes.put(byteArr);
    bytes.rewind();

    IntBuffer ints = bytes.asIntBuffer();
    int compactDigest = 0;
    for (int i = 0; i < ints.limit(); ++i) {
      compactDigest ^= ints.get(i);
    }

    return compactDigest;
}

A Sha Hash has 256 Bits e.g.

"364b7e70a9966ef7686ab814958cd0017b7f19147a257d40603d4a1307662b42"

this will exceed the range of long and integer. You could use new BigInteger( hash, 16 ); for a decimal representation.

public static void main(String[] args) throws NoSuchAlgorithmException {
        MessageDigest digest = MessageDigest.getInstance("SHA-256");
        digest.update("string".getBytes() );
        byte[] hash = digest.digest();
        BigInteger bi = new BigInteger( hash );
        System.out.println( "hex:" + bi.toString(16) + "\r\ndec:" + bi.toString() );
    }

class String has a hashcode method, like any other Java class, which transforms the string into a number. See the documentation of this method for the exact algorithm it uses.

every object in java has hashCode() method. You can override it and specify your own logic. Look at the examples.

Please find it here: http://pastebin.com/j6Cffkcp;

I but it returns only string.

Cryptographic hashes created using the JCE classes (MessageDigest in your case) are essentially a sequence of bytes (256 bits for SHA-256). If you wish to store and manage these are numbers, you'll need to convert these into BigInteger or BigDecimal objects (given the length of the digest).

It is not always that a cryptographic hash of String objects are computed, and it is often done for the purpose of one-way encryption of secrets. If you are using the hash for other purposes, especially to ensure some sort of uniqueness among the Strings (that would be important when storing these objects in a hash map), you're better off using the hash value computed by the String.hashCode method.